1. Field of the Invention
The invention relates to an image forming apparatus using an electrophotographic system, and more particularly to the apparatus in which a cover member that can be separated from its main body having an image forming means with a sheet forward path as a demarcation is implemented by a rocking frame or a moving frame.
2. Description of the Related Art
An image forming apparatus such as an electronic copying machine or a printer employs a system in which a copy is made by forming a toner image on a photoreceptor drum, transferring the toner image onto a sheet, and fusing the transferred toner image afterwards through a fuser. This image forming apparatus is also designed so that sheets are fed from a unit such as a sheet feed cassette disposed on a sheet feed section of the apparatus one by one using a sheet feeder and forwarded toward an image transfer section of the photoreceptor drum. Among such image forming apparatuses is a comparatively small image forming apparatus that is designed so that its frames can be opened and closed with a sheet forward path as a border, and, e.g., when a sheet is stopped inside the sheet forward path, one of the frames is opened to free the sheet feed path so that the jam can be taken care of with ease. Further, as described above, the image forming apparatus in which one of the frames can be opened and closed facilitates the operation of inspecting the image forming means or replacing various units, etc., by opening the frame.
In addition to the above-mentioned ordinary image forming apparatuses, some small printers are designed in such a manner that an image forming means is arranged so as to confront the printer body and that a frame is separable from the printer body with a sheet forward path as a border, so that the operation of handling jams or maintenance of the printer can be performed conveniently. In an example proposed, e.g., in Japanese Patent Unexamined Publication No. Sho. 63-244064 and the like, a printer includes: a unitized image forming member on the printer body; an opening/closing frame that can be opened and closed with respect to the printer body; and such components as a sheet forward means, a fuser, and the like so as to confront the opening/closing frame, so that the opening/closing frame can be opened to perform maintenance or jamming processing inside the sheet forward path.
However, in the above-mentioned conventional printer, a forward roller unit of the sheet forward path is provided integrally with the opening/closing frame. As a result, jammed sheets are left nipped between the forward rollers under strong nip pressure, thus making the operation of removing the jammed sheets cumbersome. Further, if a means for supporting only one of the forward rollers with respect to the opening/closing frame is provided, the jamming can be handled easily, but the roller becomes an obstacle, e.g., to taking the image forming member out.
To overcome the above problems, a printer is proposed, e.g., in Japanese Patent Unexamined Publication No. Hei. 1-314256. In this printer, when opening the opening/closing frame with the sheet forward path as a demarcation, its fuser is left on the printer body side and only a part of the sheet forward path is opened. However, the thus constructed opening/closing frame is to be opened with the forward roller unit of the sheet forward path nipping a sheet therebetween, thus leaving the jam handling problem unsolved.